Although DNA vaccines offer many advantages, their inability to elicit sustained protective immune responses in non-human primates and humans has been disappointing. Based on substantial evidence derived from tumor model systems and preliminary studies with a candidate Plasmodium yoelii vaccine, this proposal hypothesizes that an effective DNA-based vaccine against malaria can be developed by expressing malarial protein antigens as fusion proteins linked to chemokine ligands for receptors on immature dendritic cells (iDC). This vaccine model differs from related approaches in that it attracts the appropriate antigen-presenting cell to the inoculation site and by fusing the vaccine epitopes of interest to the chemokine, ensures the efficient uptake of the antigen for processing. This hypothesis will be tested in a murine model of Plasmodium yoelii infection and immunogenicity. Specifically, we will 1. Evaluate ex vivo the responses elicited in BALB/c mice by a candidate multi-epitope DNA vaccine administered by in vivo electroporation that targets the pre-erythrocytic stages of P. yoelii. The candidate vaccine to be evaluated will consist of a plasmid that expresses macrophage inflammatory protein 31 (MIP- 31) fused to (a) The SYVPSAEQI immunodominant P. yoelii Class I-restricted T cell epitope in BALB/c mice (b) The (QGPGAP)4 immunodominant P. yoelii B cell epitope in BALB/c mice and (c) The YNRNIVNRLLGDALNGKPEEKA immunodominant Class II-restricted T cell epitope in BALB/c mice. A similar DNA construct will be created that lacks the MIP-31 component and several additional positive and negative control immunization groups will also be established. Outcomes of immunization will be measured by interferon gamma (IFN-3) Elispot assays, antibody concentrations measured in ELISA and immunofluorescence assays, and by flow cytometry evaluation the development of central memory T cells. 2. Evaluate the protective efficacy of this candidate vaccine in mouse malaria challenge models. Outcomes will be followed using real-time PCR to quantitate malaria gene expression in liver samples from the mice and levels of blood parasitemia attained in immune compared to nonimmune mice. PUBLIC HEALTH RELEVANCE: This project is designed to develop a vaccine for malaria. Should this approach be successful, this vaccine could save the more than 1 million deaths that occur annually as a result of this infection.